Schema change detection

A state listener registered with Cluster object will be notified of schema changes.

There are three types of changes – keyspace_created, keyspace_changed and keyspace_dropped. All will be communicated to a state listener using its accordingly named methods with a Keyspace instance as an argument.

Background

Given

a running cassandra cluster

And

a file named “printing_listener.rb” with:

class PrintingListener
  def initialize(io)
    @out = io
  end

  def keyspace_created(keyspace)
    @out.puts("Keyspace #{keyspace.name.inspect} created")
  end

  def keyspace_changed(keyspace)
    @out.puts("Keyspace #{keyspace.name.inspect} changed")
  end

  def keyspace_dropped(keyspace)
    @out.puts("Keyspace #{keyspace.name.inspect} dropped")
  end
end

And

the following example:

require 'printing_listener'
require 'cassandra'

listener = PrintingListener.new($stderr)
cluster  = Cassandra.cluster

cluster.register(listener)

$stdout.puts("=== START ===")
$stdout.flush
$stdin.gets
$stdout.puts("=== STOP ===")
$stdout.flush

And

it is running interactively

And

I wait for its output to contain “START”

Listening for keyspace creation

Given

an empty schema

When

I execute the following cql:

CREATE KEYSPACE new_keyspace WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 3}

And

I close the stdin stream

Then

its output should contain:

Keyspace "new_keyspace" created

Listening for keyspace drop

Given

the following schema:

CREATE KEYSPACE new_keyspace WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 3}

When

I execute the following cql:

DROP KEYSPACE new_keyspace

And

I close the stdin stream

Then

its output should contain:

Keyspace "new_keyspace" dropped

Listening for keyspace changes

Given

the following schema:

CREATE KEYSPACE new_keyspace WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 3}

When

I execute the following cql:

CREATE TABLE new_keyspace.new_table (id timeuuid PRIMARY KEY)

And

I close the stdin stream

Then

its output should contain:

Keyspace "new_keyspace" changed